Influence of GPS antenna phase center variation on precise positioning

The GPS antenna is the connecting element between the GPS satellites and the GPS receiver. It receives the incoming satellite signal and then converts its energy into an electric current, which can be managed by the GPS receiver. The accurate antenna phase center offsets’ values and phase center variation factors are critical issues in GPS precise positioning. Some GPS users simply apply the manufacturer’s recommended offset values which may not match the precise values determined by calibration process. Other users may ignore the phase center correction factors during GPS data processing. In both cases, the resulted coordinates will have errors especially the height component.In this study, some static and kinematic field experiments have been carried out to evaluate the effect of using the manufacturer’s recommended antenna phase offset and ignoring its variation on precise positioning. The GPS data have been post-processed by two commercial software. The results showed that, a significant error may occur in case of disregarding the calibrated values and applying the manufacturer’s recommended ones. Investigation is also made on the effects of mixing different types of antennas. Significant variations are observed on the height components than the associated horizontal component due to phase center variation. The maximum variations are reached about 8 and 4 cm in height and northing components respectively.